In recent years, there are many vehicles equipped with navigation devices configured to provide travel guidance of the vehicles for drivers to be able to easily reach desired destinations. Herein, such a navigation device is a device that can detect the current position of a vehicle equipped therewith by a GPS receiver, for example, and can acquire map data corresponding to the current position from a recording medium such as a DVD-ROM or a HDD or through a network to display the map data on a liquid crystal monitor. Furthermore, this navigation device has a route search function of searching for a recommended route from the current vehicle position to a desired destination when the desired destination is input. The navigation device sets a recommended route thus found as a guidance route, displays the guidance route on a display screen, and also provides audio guidance when, for example, the vehicle approaches an intersection, thereby reliably guiding a user to the desired destination. In recent years, some of mobile phones, smart phones, tablet terminals, and personal computers, for example, have the same functions as that of the navigation device.
In recent years, as a traveling mode of a vehicle, other than manual traveling in which a vehicle travels based on driving operation of a user, traveling by automated driving control has been newly proposed that causes the vehicle to travel in an automated way along a preset route without driving operation of the user. In the automated driving control, for example, the current position of the vehicle, the lane in which the vehicle is traveling, and the positions of other vehicles there around are detected at any time, and vehicle control of the steering, the drive source, and the brake, for example, is automatically performed such that the vehicle travels along the preset route. Although traveling by the automated driving control can advantageously reduce the driving burden on a user, there are situations in which road conditions make it difficult to cause the vehicle to travel by the automated driving control. For example, there are situations in which the vehicle needs to change lanes or merge into another lane in a short section or travel in bad weather. In such situations, the vehicle needs to interrupt traveling by the automated driving control and shift to manual driving.
In view of this, the navigation device described above, for example, is newly required to search for a recommended route in consideration of interruption of the automated driving control described above. For example, in order to cause a vehicle to travel by automated driving control without being interrupted, Patent Document 1 proposes a technique of classifying a road having low accuracy of the current position detected by the GPS as an automated-control inapplicable road on which the vehicle cannot travel by the automated driving control, and searching for a route avoiding the automated-control inapplicable road.